Systems and methods for inferring fuel vapor canister loading rate

Abstract

Methods and systems are provided for indicating a restriction in a fuel system vapor recovery line. Responsive to such an indication, methods and systems are provided for taking mitigating actions such that an entirety of a vehicle fuel system and evaporative emissions system, including a fuel filler system, may be diagnosed as to a presence or absence of undesired evaporative emissions, even with the restriction in the vapor recovery line present. In this way, undesired evaporative emissions may be reduced or avoided, completion rates for such tests may be increased, and customer satisfaction may be improved.

The invention claimed is: 
     
       1. A method, comprising:
 monitoring a fuel dispense rate of fuel into a fuel tank positioned in a fuel system of a vehicle during a refueling event; 
 monitoring pressure in a vapor recovery line configured to circulate and/or hold a percentage of refueling vapors during the refueling event; 
 indicating a restriction in the vapor recovery line based on an expected pressure in the vapor recovery line differing by a threshold amount from monitored pressure during the refueling event, where the expected pressure is based on the fuel dispense rate; and 
 adjusting entry conditions for conducting a test for a presence or absence of undesired evaporative emissions on the fuel system and an evaporative emissions system of the vehicle responsive to the restriction in the vapor recovery line being indicated. 
 
     
     
       2. The method of  claim 1 , wherein adjusting entry conditions further comprises:
 indicating conditions are met for conducting the test for the presence or absence of undesired evaporative emissions on the fuel system and evaporative emissions system provided that at least a fuel level in the fuel tank is below a fuel level threshold. 
 
     
     
       3. The method of  claim 2 , where the fuel level threshold is below a valve positioned in the fuel tank, where the valve is configured to open under negative pressure in the fuel tank, and where the valve is coupled to a fuel filler neck. 
     
     
       4. The method of  claim 1 , wherein the test for the presence or absence of undesired evaporative emissions further comprises:
 sealing the fuel system and the evaporative emissions system; 
 fluidically coupling the fuel system to the evaporative emissions system; 
 applying a negative pressure on the fuel system and the evaporative emissions system; and 
 indicating the presence of undesired evaporative emissions responsive to the negative pressure in the fuel system and the evaporative emissions system not reaching a threshold negative pressure during applying the negative pressure. 
 
     
     
       5. The method of  claim 1 , wherein indicating the restriction in the vapor recovery line further comprises setting a malfunction indicator light to notify a vehicle operator of a need to service the vehicle, and wherein the test for the presence or absence of undesired evaporative emissions includes when the vapor recovery line is degraded and when the vapor recovery line is not degraded. 
     
     
       6. The method of  claim 1 , further comprising, during the refueling event, indicating a canister load of a fuel vapor canister positioned in the evaporative emissions system, where indicating the canister load is a function of the fuel dispense rate and the monitored pressure in the vapor recovery line.